It's probably crud caught in the throttle body plugging up the AIS motor and the bleed air hole which allows it to sustain idle and delay RPM drop. Get some -throttle body cleaner- and soak a bunch of it in there, then run the engine and while slightly reving it (enough to keep it moving, the cleaner will want to stall it) spray into the TB and the holes\galleys in it. That fixes alot of issues like this and it only takes 10mins, 3$, and if it doesn't work it didn't cost a ton and probably needed to be done anyways.
My jeep has only ever killed 3 things, a cat, a deer, and my wallet. What's the problem officer?
1992 Red YJ. Lifted, locked, and loaded with beer (Disclaimer: This doesn't mean said driver endorses drinking and driving, please enjoy alcohol responsibly and do not operate any vehicle of any kind, thank you....)
Thanks to the price of gas here ($4.25 a gal) I just bought a mountain bike, 0" of lift, 0" of travel, MT's, locked rear axle, oh yeah, it's the sh#$.